Allen and Greenough's New Latin Grammar for Schools and Colleges
J. B. Greenough, G. L. Kittredge, A. A. Howard, Benj. L. D'Ooge, Ed.

1. vir summae virtūtis, a man of the highest courage. [But not vir virtūtis .]
2. māgnae est dēlīberātiōnis, it is an affair of great deliberation.
3. “ māgnī formīca labōris ” (Hor. S. 1.1.33) , the ant [a creature] of great toil.
4. “ille autem suī iūdicī ” (Nep. Att. 9) , but he [a man] of independent (his own) judgment.

[*] Note.--Compare Ablative of Quality (§ 415). In expressions of quality, the genitive or the ablative may often be used indifferently: as, praestantī prūdentiā vir, a man of surpassing wisdom; maximī animī homō, a man of the greatest courage. In classic prose, however, the genitive of quality is much less common than the ablative; it is practically confined to expressions of measure or number, to a phrase with êius , and to nouns modified by māgnus , maximus , summus , or tantus . In general the Genitive is used rather of essential, the Ablative of special or incidental characteristics.

[*] a. The genitive of quality is found in the adjective phrases êius modī , cûius modī (equivalent to tālis, such; quālis, of what sort):—

êius modī sunt tempestātēs cōnsecūtae, utī; (B. G. 3.29), such storms followed, that, etc.

[*] b. The genitive of quality, with numerals, is used to define measures of length, depth, etc. (Genitive of Measure):—

1. fossa trium pedum, a trench of three feet [in depth].
2. mūrus sēdecim pedum, a wall of sixteen feet [high].

For the Genitive of Quality used to express indefinite value, see § 417.

Partitive Genitive